Variable waveguide coupler



Aug. 4, 1959 Filed June 26, 1957 W. G. HEINARD ET AL VARIABLE WAVEGUIDE COUPLER 2 Sheets-Sheet 1 IN VEN TORJ Whilden G. Heinard BY Howard S. Jones,Jrz

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Aug. 4, 1959 Filed June 26, 195'? w. G. HEINARD ET AL 2,898,559 VARIABLE WAVEGUIDE COUPLER 2 Sheets-Sheet 2 INVENTORS, Whilden G. Heinard BY Howard S. Jones Jn f. *T 52. 27%; ,Q.

nited States Patent fiice 2,898,559 Patented Aug. 4, 1959 VARIABLE WAVEGUIDE COUPLER Whilden G. Heinard, Kensington, Md., and Howard S. Jones, Jr., Washington, DC, assignorsto'the United States of America as represented by the Secretary of the Army Application June 26, 1957, Serial No. 668,264

2 Claims. (Cl. 333-I) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty there- This invention relates to waveguide directional couplers, and more particularly to a variable microwave energy directional coupler.

An object of this invention is to provide a waveguide coupler wherein selective microwave energy directivity is attained.

Another object is to provide a selectively variable microwave energy excitation from a transmitting waveguide to a coupled waveguide.

Still another object is to provide a selectively variable microwave energy excitation between a longitudinally disposed transmitting guide and a transversely extending waveguide coupled thereto.

A further object is to provide a microwave directional coupler which may be selectively adjusted to provide the desired microwave energy transmission to a coupled waveguide having preset axes from a transmitting wave guide having preset axes.

Still a further object is to vary microwave energydirectivity from a transmitting waveguidehaving particular axes.

The foregoing objects are achieved by interposing a displaceable plate between a main transmitting waveguide and an auxiliary coupled waveguide. This plate is pro vided with slotted apertures and is disposed in correspond ingly shaped recessed portions in selected walls of the waveguides to act as a common wall segment therefor.

Suitable adjustment of the intermediate plate results in a proportionate change in the energy coupled into both the arms of the auxiliary waveguide.

The specific nature of the invention as well as other objects, uses and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

Figure l is a perspective view of the waveguide directional coupler of the present invention with certain parts broken away.

Figure 2 is a partial plan view of the coupler of Figure 1 with a displaceable plate in one position with respect to the waveguides.

Figure 3 is a partial plan view similar to Figure 1 with the displaceable plate in another position with respect to the waveguides.

Figure 4 is a perspective view of an alternate arrangement of the coupler of Figure 1.

Referring to Figure l, numerals 10 and 12 designate the main waveguide and auxiliary waveguide, respectively. Their cross-sectional geometry is preferably rectangular and identical in most respects, and as illustrated in Figures 1-3, guides 10 and 12 may be disposed normal to each other in some practical applications. As in conventional practice, the electric lines of force, established upon excitation by microwave propagation through guides 10 and 12, are preferably perpendicular to the wider dimensioned walls of the waveguides. The microwave propagation through guide 10 may be taken, for illustration purposes, to be in the direction of arrow 13.

Main guide 10 may be provided with flanges 14 and 16 for connection with similar flanges of a transmission line of a microwave system. Likewise, guide 12 may present flanges 18 and 20 for connection with similar flanges of utilization apparatus (not shown). As an alternative modification, pick-up probes (not shown) may be suitably mounted within the walls of arms 22 and 24 of auxiliary waveguide 12 and arm 26 of main waveguide 11 to satisfy some desirable requirements. Additionally, arm 26 of guide 10 and either of the arms 22 and 2d of guide 12 may be fabricated to function as a microwave absorbing section by suitably incorporating therein conventional resistance strip means.

The main guide 10 and the auxiliary guide 12 are preferably assembled with one of the wider walls of each lying substantially in the same plane or in planes that may be slightly spaced from one another. At the intersection of the longitudinal axis of guides 10 and 12 and symmetrical with their common transverse axis that is normal to the aforementioned planes is a displaceable plate 28. As shown, displaceable plate 28 may assume the form of a disk which is adapted to be rotatably fitted in correspondingly shaped recesses 30 and 32 in the waveguides 10 and 12, respectively. Guides 10 and 12 and plate 28 are adapted to be rotatably displaced one rela tive to another. Accordingly, plate 28 will function as a common wall for both main guide 10 and auxiliary guide 12.

Elongated slots or apertures 34 and 36 extend through plate 28 to provide the necessary electromagnetic coupling between main guide 10 and auxiliary guide 12. As is well known, primary microwave energy transmission in the main waveguide 10 may now be able to excite secondary microwave energy in auxiliary waveguide 12. The magnitude of this energy transfer is of course dependent on such factors as the microwave frequency, the thickness of the plate 28, the size and shape of coupling apertures 34 and 36, and the relative positioning of the axes of the coupling apertures 34 and 36. However, for a suitably chosen pair of coupling apertures the dependency of energy transfer upon the change in microwave frequency is relatively small. Additionally, the amount energy excitation in either arm 22 and 24 of auxiliary guide 12 will assume a definite proportion of the microwave energy transmission in main guide 10. These amounts may be readily predetermined with reasonable accuracy from empirical, graphical or mathematical analysis.

Referring now to Figures 1 and 2, elongated apertures 34 and 36 may have their major axes parallel to and on dilferent sides of the longitudinal axis of main guide 10. Hence, apertures 34 and 36 will extend in the direction of the primary wave energy transmission in main waveguide 10. The peculiar disposition of the coupling slots will give rise to excitation of secondary wave energy of a particular magnitude in arm 22 of auxiliary guide 12 in the direction indicated by arrow 38 (Figure 2). A relatively small amount of microwave energy will be induced in arm 24 of auxiliary guide 12 and if desired it may be considered negligible. Suitable conventional energy absorbing means may be provided in arm 2% or the energy may be permitted to be dissipated along the length of arm 24 or into any attached waveguide component.

When plate 28 is rotated sufiiciently, as in Figure 3, so that elongated apertures 34 and 36 are perpendicular to the longitudinal axis of main waveguide 10, the

primary microwave energy in main waveguide will excite secondary microwave energy having a particular magnitude in arm 24 of auxiliary guide 12 in the direction of arrow 40. Again, the amount of energy excited in arm 22 is relatively small and may be considered negligible for most practical application. If it be significant in amount and undesirable a microwave absorbing means may be incorporated in arm 22.

If it be desirable to excite microwave energy through arms 22 and 24 of auxiliary waveguide 12 in amounts between the maximum and minimum contemplated by the present invention, plate 28 may be rotated through a suitable angular displacement. Hence, by empirical determination, a specific plate may be properly calibrated to represent a specific microwave combination induced in arms 22 and 24, respectively, of waveguide 12 upon a particular controlled orientation or displacement of calibrations 42 with respect to index 44.

In some applications of the instant directional coupler, it may be desirable to secure waveguide 10 to waveguide 12 by clamping or the like, to prevent angular rotation or displacement therebetween so that one can be maintained in a normal position with respect to the other. In this position, plate 28 will be rotatable with respect to both guides 10 and 12.

A further significant application of this invention resides in the fact that high directivity may be obtained at a particular microwave frequency, by a suitable angular adjustment of the microwave coupler components. Thus, with slots 34 and 36 of plate 28 positioned as illustrated in Figures 1 and 2, and with auxiliary waveguide 12 free to rotate through an angular displacement with respect to guide It while fulcrumed about plate 28, variations in induced microwave energy are possible in guide 12. Accordingly, with both auxiliary waveguide 12 and plate 28 free to rotate with respect to main waveguide 10, many variations and combinations of directivity and excited wave energy in auxiliary waveguide 12 are made possible for numerous desirable applications (Figure 4).

It will be appreciated by those skilled in the art that the present invention is not restricted to any size of Waveguide and plate. An extremely desirable replacement for stock sizes of fixed couplers is attained and is capable of use with high power sources. Similarly, the instant coupler may be calibrated to function as a limited range variable attenuator.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

We claim:

1. A microwave energy coupler comprising in combination: first and second intersecting lengths of rectangular waveguide having their wider walls adjacent and substantially coplanar, and a displaceable disc interposed at the intersection of said wider walls parallel thereto and rotatably fitted in correspondingly shaped recesses in said wider walls so that said disc functions as a common wall capable of being rotatably displaced about an axis perpendicular to said disc, said disc having two spaced elongated apertures adapted to be symmetrically disposed on either side of the longitudinal axis of said first and second lengths of waveguide upon predetermined rotations of said plate, said first and second lengths of waveguide being adapted to be rotatably displaceable with respect to one another about said axis independently of the rotation of said disc, the rotation of said disc and said lengths of waveguide permitting the direction and amount of the energy coupled between said first and second waveguides to be varied.

2. The invention in accordance with claim 1, wherein said disc is provided with calibration markings to facilitate obtaining a desired degree of coupling.

References Cited in the file of this patent UNITED STATES PATENTS 2,634,332 Zaleski Apr. 7, 1953 2,702,884 Riblet Feb. 22, 1954 2,751,556 Tomiyasu June 19, 1956 2,766,431 Barker Oct. 9, 1956 

